Office for Nuclear Regulation

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System Based Inspection (SBI) of First Generation Magnox Storage Pond (FGMSP) Bulk Sludge Retrieval System (BSRS) on Sellafield Ltd's nuclear licensed sites at Sellafield

Executive summary

Purpose of intervention

The Office for Nuclear Regulation (ONR) undertakes all regulatory interaction with the Sellafield site licensee (Sellafield Limited, SL) against a strategy defined by ONR's Sellafield Programme. In accordance with that Strategy, a System Based Inspection (SBI) of the First Generation Magnox Storage Pond (FGMSP) Bulk Sludge Retrieval System (BSRS) was planned and undertaken in March 2017. The purpose of this inspection is for ONR to examine whether the licensee's safety case claims in respect of this system important to safety have been adequately implemented.

The scope of this inspection activity comprised the Bulk Sludge Retrieval Tool (BSRT), the Deluge Skip Wash Box (DSWB), the Pond 2 Booster Pump Platform (Pond 2 BPP), the Pond 3 Booster Pump Platform (Pond 3 BPP), and the associated booster pumps, valves, instrumentation and connections to the retrievals tool, the sludge transfer line to the Sludge Packaging Plant 1 (SPP1) and the effluent (supernate) return line from SPP1. The BSRS is important to nuclear safety as it enables the safe removal of radioactive sludge currently stored in the FGMSP pond to a modern purpose built plant, SPP1, thereby delivering an important part of the hazard and risk reduction operations in FGMSP and across the site more generally.

ONR's SBI process examines evidence to determine compliance against six key licence conditions (LCs). These licence conditions (listed below) have been selected in view of their relevance to ensuring nuclear safety and in providing a structured approach to determining whether the safety case has been implemented adequately through the system being inspected.

Interventions Carried Out by ONR

I carried out this SBI over the course of two days. I was assisted by three ONR specialist inspectors with expertise in the fields of mechanical engineering, liabilities, and fault studies respectively. I was also supported on this inspection by SL staff from its internal regulatory organisation and the Decommissioning Safety Representative. The inspection comprised discussions with SL staff, physical viewing and inspections of targeted structures, systems and components, and review of SL's records and other safety documentation.

Explanation of Judgement if Safety System Not Judged to be Adequate

I judge the safety case supporting this system to be adequately implemented.

Key Findings, Inspector's Opinions and Reasons for Judgements Made

From the areas I targeted and the evidence I examined during this inspection, I consider that SL has adequately implemented those safety case claims that relate to the BSRS. In particular, SL has undertaken a significant amount of work to ensure that operators are adequately trained to ensure the system is operated within clearly defined limits and conditions. SL has also provided evidence of a comprehensive set of operating instructions which, in my opinion, should facilitate the safe operation of the currently commissioned system. I judge SL's emphasis of the importance of clear lines of command and control for the BSRS to be evidence of relevant good practice. As such I award inspection ratings of Green (No Formal Action) for LCs 10, 23, and 24.

I also identified four areas for improvement. The first relates to safety mechanisms. Although SL presented some examples of good practice, ONR identified that the hard wired alarm, whilst operational, has the incorrect colour light installed in annunciator panel 8. This equipment is required to alert FGMSP operators to a leak from primary containment. Furthermore, SL needs to clarify the sampling required if such a leak is detected. In general, there was evidence of adequate, regular and systematic examination inspection, maintenance and testing. However SL is still in the process of transferring maintenance from commissioning to operations and I judge that although SL is complying with its legal duties there are two minor contraventions of specific administrative requirements. However, overall I judge these to be minor shortfalls. As such I award inspection ratings of Green (No Formal Action) for LCs 27, 28 and 34.

In the course of my inspection I did not identify any significant concerns with the adequacy of the licensee's safety case for this system that would necessitate an earlier than planned assessment by ONR.

Conclusion of Intervention

I consider that the licensee has a good knowledge of the physical condition of the structures, systems and components reviewed during this inspection and have in place appropriate management controls to ensure on-going safety.

I have, however, identified four areas for improvement, which are minor in nature when compared with appropriate benchmarks. I have therefore raised four ONR Regulatory Issues at Level 4 to track SL's responses to questions of detail raised in the inspection.

Overall, on balance therefore, I consider the safety case supporting this system to be adequately implemented.